Use the new JSON API
The new JSON API has landed in Drupal core. We should leverage it in Aegir5.
For example, we have a custom route/class/method to ingest the logs from running Ansible on the backend. I think we do something similar in a couple other places too. We probably want to push this back through the queue (to more easily allow for multi-server scenarios) but a worker on the control VM could maybe leverage the json api for the "last mile".
Also, of course, all the SaaS-enabled stuff should be much simpler if we don't need all the overhead of the Services module.